Mechanical Properties of the Sol-Gel Derived Alumina-Bovine Hydroxyapatite Composites


YELTEN A. , YILMAZ S.

19th International Biomedical Science and Technologies Symposium (BIOMED 2013), Aydın, Turkey, 12 - 15 November 2013, pp.63

  • Publication Type: Conference Paper / Summary Text
  • City: Aydın
  • Country: Turkey
  • Page Numbers: pp.63

Abstract

Sol-gel technology is an ideal way to produce powder materials with high chemical purity. Alumina (α-Al2O3) is commonly used in strength-based biomaterial applications due its bioinert character. Although hydroxyapatite (HA, Ca10(PO4)6(OH)2) can form biochemical bonds with body tissues, its solo usage is not suitable because of its brittle nature.

Boehmite sol was produced via the sol-gel procedure. Aluminum isopropoxide (AIP, Al(OC3H7)3) was used as the starting material and hydrolyzed in a system where distilled water/AIP molar ratio was 100. BHA powders (bovine hydroxyapatite) obtained from bovine bones were added as 10, 20, 30 and 50 wt.% of AIP to the boehmite sol and mixed. Partially homogeneous dispersion of BHA powders in the sol was provided utilizing from sodium alginate (Na-alg, NaC6H7O6). Following gelation at 110 °C for 3 hours, heat treatment was applied to the gelated mixtures at 1300 °C for 2 hours and eventually composite powders comprised of α-Al2O3 with high purity and crystallinity, HA and tricalcium phosphate (TCP, Ca3(PO4)2) phases were obtained. Chemical analyses of the composite powders were done with a Rigaku D/Max-2200/PC branded x-ray diffraction (XRD) device. Composite powders were coded as 1300AH10, 1300AH20, 1300AH30 and 1300AH50 where 1300 stands for the heat treatment temperature, A for the α-Al2O3 and H for the BHA phase while 10, 20, 30 and 50 for the BHA powder amount (wt.%) added to the sol. Cylindrical pellets were prepared from each composite powder group by pressing and sintering at 1300 ºC for 2 hours. Cold compression tests were performed on the pellets by using a Devotrans branded DVT FU model device. Fracture surface characterizations were carried out with a Jeol branded JSM 6335F (field emission) model scanning electron microscope (SEM).
 
Compression test results showed that the compression strength and Young’s modulus values of the composite pellets increased with increasing amount of BHA powder added to the boehmite sol. 1300AH50 sample exhibited the highest average compression strength, 114 MPa.
 
Compression test results were considerably lower than that of the α-Al2O3 phase itself. It is thought that the ceramic bonds formed between α-Al2O3 and BHA phases are not strong enough due to insufficient sintering time and temperature. Fracture surface SEM images indicated that the fractures occurred at the grain boundaries, α-Al2O3 crystals could not grow and large pores and gaps exist between the α-Al2O3 and BHA grains.